Optical coherence tomography (OCT) is an imaging technique that makes possible the three dimensional imaging of transparent or semi-transparent objects, such body tissues, specifically eye. OCT is described in detail in U.S. Pat. No. 6,769,769, the contents of which are herein incorporated by reference.
Using Optical Coherence Tomography (OCT) it is possible to rapidly obtain a line of image information extending in the z direction, where the z axis extends in the depth direction. Such a scan is known as an A-scan. In time domain OCT, this can be done by changing the optical path difference between the reference beam and object beam in the interferometer to cause the “coherence gate,” or region where the optical path difference is less than the coherence length, to move back and forth in the depth direction. Image information is obtained from the position of the coherence gate. In spectral OCT, by analyzing the spectrum of the returned signal, a complete line of information in the z direction can be obtained from a signal measurement.
By moving the interferometer beam along the x or y axes (or any other plane orthogonal to the x-y plane), it is possible to obtain a B-scan. This is a sectional scan through the sample in the depth direction.
These depth images, or B Scans, can in turn be collected in a raster pattern to obtain a volume image of the tissue. However, in the case of imaging the eye, which is an important application of OCT, patient movement due to breathing, heartbeat, inability to fixate, or any other reason causes the captured B Scans to be mis-aligned.